It is now well known to perform a variety of surgical procedures by the introduction of an interventional device into the body, for example, into an arterial or venous blood vessel, or into a laparoscopic or other cavity artificially maintained in the body. Typical of the former type of procedure are coronary angiography (e.g., where an X-ray contrast fluid is inserted into the coronary artery) and percutaneous transluminal coronary angioplasty (PTCA). These and other procedures involve the introduction of an interventional device, such as a catheter (open or closed end), a wire guide, a balloon, a stent, an atherectomy device, or the like into the vessel or cavity in question. The devices may be non-implantable and removed following the procedure or shortly thereafter. Alternatively, the devices may be implantable, remaining in the vessel of the patient post implantation.
Procedures for introducing a catheter into a blood vessel include the cut-down method and the Seldinger technique. The Seldinger technique is well known, and first involves opening a blood vessel with a needle, inserting a guide wire into the vessel through the lumen of the needle, withdrawing the needle and inserting a dilator over the guide wire. The dilator is located inside an associated sheath which is also inserted into the vessel, and the dilator is sealed to the sheath by a hemostasis or hemostatic valve through which the dilator passes. The dilator is removed, and the catheter inserted through the sheath and into the vessel.
The catheter may include a balloon on the distal portion thereof. The tip of the catheter is advanced to the site of treatment, for example, an atherosclerotic plaque, the balloon being deflated during the insertion. Once in position across the treatment site, the flexible, expandable, preformed balloon is inflated. The inflated balloon may be used, for example, to relieve stenosis at the atherosclerotic plaque, at least partially. Typically, the balloon is inflated by supplying a pressurized fluid through an inflation lumen in the catheter. The balloon catheter may also be used for delivering a medical device such as an intravascular stent to a treatment site. After completion of the procedure, the balloon is deflated to a small profile so that the catheter may be withdrawn from the patient's vasculature and blood flow resumed through the dilated vessel.
Currently, inflation and deflation of the balloon occur at the same rate. Rapid inflation of the balloon may damage vessels or provide less precision in the placement of an implantable medical device, such as an intravascular stent. Rapid deflation of the balloon is desirable to prevent prolonged occlusion of blood flow in the vessel. Valves for use with medical devices have previously been used for flow control by preventing flow in a first direction and allowing flow in a second direction. Therefore, it is highly desirable to provide a non-implantable valve assembly that allows different flow rates in medical devices, such as for inflation and deflation of the balloon on the catheter at the site of treatment. The non-implantable valve assembly of the present invention will allow variation in flow, providing a slower flow rate in a first direction and a more rapid flow rate in a second direction.